Bearing alloy



Patented May 9, 1939 PATENT OFFICE 2,157,121 BEARING ALLOY Ernest R. Darby, Lawrence A. Barera, and Philip J. Potter, Detroit, Mich., assignors to Federal- I Mogul Corporation, Detroit, Mich., a corporation of Michigan No Drawing. Application July 23, 1937,

Serial No. 155,218

5 Claims." (Cl. 75-166) Our invention relates to hearing alloys." It has to do particularly with a novel bearing alloy for rotating shafts designed to operate under heavy loads and at high speeds, although it is not necessarily limited thereto.

The use of relatively soft metals or alloys as bearing metals is old. One purpose of such use is to provide, as a support for the shaft, a contacting surface which will adequately support a relatively hard shaft or the like and which will, at the same time, avoid scoring or seriously abrading the shaft as it rotates within the bearing.

The metals which have been most extensively used for this purpose may be generally classed as tin-base and lead-base alloys. The tin-base alloys are mainly composed of tin, but usually contain substantial percentages of copper and antimony, increasing in hardness-as the contents of copper and antimony are increased. The leadbase alloys are mainly composed of lead, but

usually contain significant percentages of one or more of the metals, antimony, tin and copper, which generally serve to.harden the alloy.

In addition to'the tin-base and lead-base alloys, other alloys are, to a lesser extent, in use as bearing alloys. consisting of cadmium, zincand antimony, alloys of cadmium and nickel, alloys of cadmium, silver and copper and alloys of cadmium and copper. Lead, hardened with one or more alkali metals or alkaline earth metals, such as sodium, calcium, barium andlithium, have also been used as bearing alloys.

It is more or lessv generally recognized in the art that alloys which are desirable as bearing alloys should be composed of harder particles imbedded in a relatively soft matrix, or soft particles imbedded in a harder matrix, or a matrix in which both harder and softer particles are dispersed. The theory is that the harder particles serve to make the contact and directly carry the loads, while the softer particles or matrix permit the bearing alloy to conform to the shape of the moving member or shaft.

Tin-base and lead-base alloys have many desirable properties. However, they have certain drawbacks which are particularly noticeable in hearing service in the automotive industry. I They have a fair degree of strength, but there is considerable room for improvement. Also, they are comparatively low in ductility which is one of the drawbacks thereof. Likewise, they have a comparatively low melting point, which is an'undesirable characteristic. With constantly increasing speeds and pressures to which bearings are These include cadmium-base alloys being subjected when used in the automotive industry, tin-base and lead-base bearings show a tendency to fail either by cracking or squashing out after comparatively short periods of service.

Considerable efiort has been made to produce 5 bearing alloys which are stronger, have greater ductility and have higher melting points than the tin-base or lead-base alloys. Some of the cadmium-base alloys mentioned above possess these relative advantages. However, these cad- 10 mium-base alloys possess other disadvantages. For one thing, under present market conditions, there is a shortage of supply of cadmium, which not only materially increases the cost but even makes dimcult the obtaining of an adequate supply of cadmium to fill the demand for bearing alloys of the type in question.

' ing point.

Another object of this invention is to provide a bearing alloy which will possess most, if not all, 25 of the advantages of the best cadmium-base bearing alloys, but which will have substantially lower percentages of cadmium and which will utilize other metals instead which are relatively inexpensive, and more readily available.

Other objects and advantages of our invention will appear as thisdescription progresses.

Our invention contemplates the production of a bearing alloy wherein the primary ingredient is lead. Cadmium is used. However, the per- 35 centage of cadmium used is markedly decreased in comparison with the so-called cadmium-base alloys, so that the cost of the alloy, is greatly decreased and the question of availability of cadmium becomes a less important factor. Our alloy 40 also preferablycontains silver and antimony in percentages and for purposes which will be subsequently made clear.

At the present time, we have good reason to believe that, considering the various possible services for bearing alloys, metals containing from 66.5 to 94.25 per cent lead, from 5 to25 per cent cadmium, from .5 to 6 per cent silver and .25 to 2.50 per cent antimony will be suitable as hearing alloys when the percentages are adjusted to fit the particular type of service for which they are designed. Therefore, alloys having these ranges of percentages are within the scope of our invention. 5

Our tests to date, however, indicate that the 55 alloys which we shall prefer to use'for bearings tin base alloys both from the standpoint of strength and high melting point, and, likewise, from he standpoint of much greater ductility.

We have made a. number of tests of lead-base alloys containing cadmium, silver and antimony, with the lead and other elements present in varying percentages. Our investigations have been so extensive that it is not feasible to recite the results obtained in all of the tests. However, a comparison of one of our preferred alloys with a standard lead-base bearing alloy, with particular reference to physical properties, will illustrate the superiority of our type of alloy thereover. Such a comparison will be found. in the following not care to be bound by any theories. However, it may be pertinent here to say that our initial tests had to do with lead-base alloys containing cadmium and silver and also lead-base alloys merely containing cadmium in addition to the lead. Tests of these alloys for various physical properties showed that, as cast, they possess adequate hardness and ductility, but that upon ageing at room temperatures, their hardness decreased to such an extent as to render them unde' sirable for use as bearing alloys. For example, these ternary and binary alloys would ordinarily show a Brlnell hardness of 22 immediately'after casting and solidification, but after being permitted to age at room temperatures for 100 hours would show a decrease to Brinell hardness of 12. The initial hardness and the final hardness, of course, varied with the constltutents of the ternary and binary alloys and with the ageing period. However, it was clear that there resulted an age-softening process which rendered the metals undesirable.

Seeking to overcome this age-softening process,

our experiments led us to the use of antimony table: in addition to the lead, cadmium and silver. As

Physical properties Brlnell hardness Tensile strength, lbs. per sq. in. Elongation percent in 2" Melting temp 212 F. 300 F. Room temp. 300 F. Room temp. 300 F.

. F. Pb 84%, 8n 6%, Sb 10% 20 9 10. 000 4. 460 Pb 73.75%, Cd 20.0%, Sb 1.25%, Ag 5.0%.. 23 to 27 8 to 11 12,000 to 14,000 5,000 to 7,000 12.5 to 20.0 20.3 to 46.8 496 Considering the Brinell hardness numbers as set forth in the above table, it will be noted. that our alloy shows a greater Brlnell hardness at room temperature than the standard lead-base alloy with which it is compared, and that its Brlnell hardness at 300 F. is substantially equal to or superior to the Brlnell hardness of the standard lead-base alloy at 212 F. The range of Brlnell hardness numbers given with relation to our alloy takes into account the fact that a greater hardness can be obtained by rapidly cooling the .alloy than by slowly cooling it, the higher Brinell strength at room temperature than the standard lead-base alloy and that the tensile strength of our alloy at 300 F. is quite high.

Likewise, the table shows, by reference to the elongation factor, that our alloy has a much greater ductility at room temperatures than the standard lead-base alloy and that this ductility increases at temperatures as'high as 300 F.

This table also shows that our alloy has a higher melting point than the standard lead base alloy with which it is compared. As noted, our alloy has a melting point of 496 F. compared with the standard lead-base alloy which has a melting point of 460 F. This comparison of melting points is, of course, variable to some extent either up or down, depending upon the percentages of the various constituents. However, it will be noted that our alloy has a definitely higher melting point than the usual lead-base alloy used a in bearing service.

We have certain theories as to the reasons why our alloy possesses the marked superiorities indicated bythe tests which we have made. We do a result of these tests, it became apparent that the antimony served to overcome this age-softening process with the result that it became possible to produce a lead-base bearing alloy having the superior properties indicated above. The particular manner in which the antimony cooperates fwith the other constituents of the alloy to bring about the desired result is more or less a matter of theory and need not be discussed here. It is sufiicient to say that when used in the proper amounts, together with the other constituents of the alloy, it results in the production of an alloy whichv will not only possess adequate hardness and other properties immediately after casting and solidification, but which will substantially retain those properties indefinitely.

It will be seen from the above that we have provided a novel and superior type of lead-base alloy. This alloy possesses greater strength and ductility than any other lead-base alloys with which we are familiar. higher melting point. These various qualities render it especially suitable for bearing alloy service and particularly for service in bearings for automotive engines. Since a comparatively small percentage of cadmium is utilized in the formation of the alloy, and since the major constituent of the alloy is lead, which is a relatively cheap material, the resultant alloy is considerably cheaper than cadmium-base bearing alloys, while possessing properties which are, as to all essentials, comparable to cadmium-base bearing alloys. Also, the smaller amount of cadmium used in the alloy solves, to a substantial extent, the problem arising from the lack of availability of cadmium in large quantities.

The alloy produced by our invention also pos- A sesses those characteristics generally considered necessary or desirable for-bearing service. Ap-

It likewise possesses 'a parently, a part of the cadmium and silver combine to form the small, hard particles. A portion of the cadmium together with a compound made up of antimony and silver goes into solid solution with the lead. This solid solution breaks down with ageing so that small, hard submicroscopic particles are precipitated and dispersed throughout the alloy with a resultant hardening effect. Thisis somewhat theoretical,

the melt with a suitable flux to prevent drossing and oxidation of the metal.

It should be understood that our invention as defined by the appended claims is intended to include alloys having the constituents enumerated but also having such percentages of impurities as may naturally occur in commercial manufacture.

Having thus described our invention, what we claim is: p Y

1. A hearing metal alloy consisting of .25 to 2.50 per cent antimony, from .5 to 6 per cent silver, from 5 to per cent cadmium and from 66.5 to 94.25 per cent lead.

2. A hearing metal alloy consisting of from to 1.50'per cent antimony, from 2.50 to 5 per cent silver, from 1'1 to 23 per cent cadmium, and from 70.50 to 79.75 per cent lead.

3. A bearing metal alloy containing 1.25 per cent antimony, 5 per cent silver, 20 per cent cadmium, and the balance lead plus impurities.

4. A bearing metal alloy containing from .25 to 2.50 per cent antimony, from .5 to 6 per cent silver, from 5 to 25 per cent cadmium, and the balance substantially all lead, said alloy having Brinell hardness at room temperature greater than 20, having a tensile strength at room temperature greater than 10,000 and a melting point higher than 460 F.

51A bearing metal alloy containing from .75 v

to 1.50 per cent antimony, from 2.50 to 5 per cent silver, from 1'7 to 23 per cent cadmium, and the balance substantially all lead, said alloy having a Brinell hardness at room temperature greater than 20, having a. tensile strength at room temperature greater than 10,000 and a melting point higher than F. v

' ERNEST R. DARBY.

LAWRENCE A. BARERA. PHILIP J. POTTER. 

